Temperature measurement device

ABSTRACT

A temperature measuring device includes a temperature-responsive element that mechanically moves a first inductive assembly component relative to a second inductive assembly component in response to temperature changes. The movement of the first inductive assembly component relative to the second inductive assembly component generates a change in a local eddy current pattern that corresponds to the sensed temperature.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/400,330, entitled “Pressure Gauge Having Dual FunctionMovement Plate” and filed on Mar. 27, 2003.

TECHNICAL FIELD

This description relates to temperature measurement, and, in particular,to temperature measurement devices.

BACKGROUND

Temperature measurement gauges are commonly found in many commercial andindustrial applications. Such devices typically may use bimetallic coilsor gas-filled Bourdon tubes to sense temperature and drive a shaftconnected to a pointer. The pointer is disposed opposite a dial havingtemperature indicia thereon. Thus, a technician may read the temperatureat the gauge.

Furthermore, a variety of devices need temperature measurement forproper operation. For example, many volumetric gas flow meters requiretemperature to properly register the amount of gas passing therethrough.Such devices often use mechanical techniques to perform the temperaturecompensation.

SUMMARY

In one general aspect, a device for measuring temperature includes ahousing, a temperature-responsive element, and an inductive assembly.The temperature-responsive element is supported relative to the housingand is operable to sense temperature and to move in response totemperature changes. A first inductive assembly component is fixedrelative to the housing, and a second inductive assembly component isoperatively and movably positioned relative to the first inductiveassembly component. The second inductive assembly component is driven bymovement of the temperature-responsive element, and the movement of thesecond inductive assembly component relative to the first inductiveassembly component generates a change in a local eddy current patterncorresponding to the sensed temperature. In particular implementations,a current at a particular point in a sensing circuit is proportional tothe temperature changes causing the temperature-responsive element tomove.

Certain implementations may include a circuit board including the firstinductive assembly component. The circuit board may include a processorresponsive to generated eddy current patterns to generate a signalrepresentative of sensed temperature. In generating the signal, theprocessor may determine the movement of the temperature-responsiveelement based on the generated eddy current patterns and associate themovement with a temperature to generate the signal.

In particular implementations, the temperature-responsive elementincludes a first portion generally fixed relative to the housing and asecond portion displaceable relative to the first portion, wherein thesecond portion drives the second inductive assembly component. Thedevice may also include a visual indicator movably positioned relativeto the housing and driven by the second portion of thetemperature-responsive element to indicate temperature.

In some implementations, the second inductive assembly componentincludes a gear with a pitch ratio larger than that of thetemperature-responsive element. The gear may include a protuberance thatoperates as an inductive target in the inductive assembly.

In another general aspect, a device for measuring temperature includes acoil operable to displace in response to changes in temperature of amedium for which a temperature is to be sensed and a rotatable shaftdriven by the temperature-responsive coil. The device also includes aninductive target displaceable by the rotatable shaft and an inductorpositioned relative to the inductive target such that displacement ofthe inductive target by the rotatable shaft generates a change in alocal eddy current pattern corresponding to the temperature to besensed. The inductive target may be rotatable with the rotatable shaftand may include a plurality of radial features extending transverselyrelative to a longitudinal axis of the rotatable shaft. The coil may bea bimetallic coil including a proximal end driving the rotatable shaft.

Certain implementations may include a circuit board including an openingthrough which the rotatable shaft extends, wherein the circuit boardincludes the inductor. Additionally, the inductive target may rotate ina plane generally parallel to the circuit board.

Particular implementations include a pointer coupled to the rotatableshaft and an indicia plate fixed relative to the pointer such that thepointer rotates in a plane generally parallel to the indicia plate toindicate temperature. The inductive target may be positioned between theindicia plate and a circuit board.

Some implementations may include a microprocessor responsive togenerated eddy current patterns to generate a signal representative ofsensed temperature. The microprocessor may determine the movement of theshaft based on generated eddy current patterns and associate themovement with a temperature to generate the signal.

In certain implementations, the inductive target includes a gear with apitch ratio larger than that of the rotatable shaft. The gear mayinclude a protuberance that operates as the inductive target. The pitchratio of the gear may be approximately fifteen times larger than that ofthe rotatable shaft.

In another general aspect, temperature measurement may be facilitated bya process performed at a temperature measurement device. The process mayinclude sensing a temperature change, converting the sensed temperaturechange to mechanical movement, and converting the mechanical movement toan electrical signal representing the movement by induction. The processmay also include detecting the electrical signal and determining themechanical movement based on the electrical signal.

In particular implementations, converting the sensed temperature changeto mechanical movement may include rotating a shaft in response to thesensed temperature change.

In some implementations, converting the mechanical movement to anelectrical signal representing the movement by induction includes movingan inductive target relative to an inductor, the movement generating achange in an eddy current pattern. In certain implementations, moving aninductive target includes driving the target with a gear that has apitch ratio less than that of the inductive target.

Particular implementations may include determining a temperatureassociated with the mechanical movement. Additionally, theseimplementations may include generating a signal representing thetemperature. Determining a temperature associated with the mechanicalmovement may include determining the amount of mechanical movement.

In another general aspect, a device for measuring temperature includes atransducer, an inductive target, a circuit board, and a visualindicator. The transducer includes a temperature-responsive, bimetalliccoil and a rotatable shaft. The coil is positioned to displace inresponse to changes in temperature of a medium for which a temperatureis to be sensed. The rotatable shaft is coupled to a second end of thecoil and is driven by the coil. The inductive target is coupled to theshaft and rotated thereby. The target includes a plurality of radialfeatures extending transversely relative to a longitudinal axis of therotatable shaft. The circuit board includes an opening through which therotatable shaft extends and an inductor positioned relative to theinductive target such that rotation of the inductive target by the shaftgenerates a change in the local eddy current pattern representing theshaft rotation. The circuit board also includes a microprocessorresponsive to generated eddy current patterns to determine the rotationof the shaft, to associate the rotation with a temperature, and togenerate an electrical signal representative of sensed temperature. Thevisual indicator includes an indicia plate generally parallel to thecircuit board and a pointer fixed to the rotatable shaft relative to theindicia plate to indicate temperature, wherein the inductive target ispositioned between the indicia plate and the circuit board and thepointer rotates in a plane generally parallel to the indicia plate.

Details of one or more implementations are set forth in the accompanyingdrawings and the description below. Other features and advantages may beapparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-B illustrate an example temperature measurement device.

FIG. 2 shows a top view an example inductive target.

FIG. 3 shows a perspective view of a sheath for protecting atemperature-responsive element.

FIG. 4 shows a perspective view of another example temperaturemeasurement device.

FIGS. 5A-B illustrate another example temperature measurement device.

FIG. 6 is a flow chart illustrating a process at a temperature measuredevice.

The drawing figures are not necessarily to scale, and, in certain views,parts may have been exaggerated for purposes of clarity.

DETAILED DESCRIPTION

Temperature measurement devices include devices operable to sense atemperature to be measured, convert the temperature to a mechanicalmovement, convert the mechanical movement to an electrical signal, anddetect the electrical signal, where the electrical signal represents thesensed temperature. Thus, temperature measurement devices may produceelectrical signals that represent temperature. Other temperaturemeasurement devices, however, may have a variety of other features.

FIGS. 1A-B illustrate an example temperature measurement device 100. Asectioned, perspective view of device 100 is shown in FIG. 1A, and asectioned, side elevated view of device 100 is shown in FIG. 1B.

Device 100 includes a temperature-responsive assembly 110, a visualindicator assembly 130, and a movement-indicative signal generator 140.In operation, temperature-responsive assembly 110 generates mechanicalmovement in response to temperature changes. Based on this movement,visual indicator assembly 130 provides a visual indication of thetemperature, and signal generator 140 produces an electrical signalrepresenting the movement. Because the electrical signal represents themovement, and the movement is produced by the sensed temperature, theelectrical signal corresponds to the sensed temperature.

In more detail, temperature-responsive assembly 110 includes anelongated housing 112 having a first end 114 and a second end 116. Atfirst end 114, assembly 110 includes a stepped-down-diameter plug 118that is coupled (e.g., by welding) to one end of a bimetallic,spiral-wound coil 120. Plug 118 may also be sealingly engaged (e.g., bywelding) with housing 112. At its other end, coil 120 is coupled (e.g.,by welding) to a rotatable shaft 122. Coil 120 displaces in response totemperature changes near first end 114 and causes shaft 122 to rotate, atype of mechanical movement. Thus, coil 120 is a transducer thatconverts temperature to mechanical movement. The medium for which coil120 is sensing temperature may be a solid, a liquid, or a gas.

Assembly 110 also includes a guide 124 that secures shaft 122. As amultitude of transducer lengths are commonly seen in variousapplications, guide 124 may include multiple components properly spacedto minimize drag on shaft 122.

Visual indicator assembly 130 includes a pointer 132 and a dial 134.Pointer 132 is coupled to shaft 122 to rotate when the shaft rotates.Dial 134, which is one example of an indicia plate, is positionedrelative to pointer 132 such that rotation of shaft 122 positionspointer 132 opposite temperature indicating indicia on the face of dial134. This provides a visible indication of temperature at device 100.

Movement-indicative signal generator 140 includes an inductive target142 and a printed circuit board (PCB) 144. Inductive target 142 iscoupled to shaft 122 to rotate with the shaft. In particularimplementations, target 142 is a light-weight, metallic (e.g., stainlesssteel or aluminum) member rigidly attached (e.g., by welding) to shaft122.

PCB 144 is fixed in position relative to shaft 122, behind dial 134. PCB144 may be coupled to assembly 110 to minimize case strains, which mayaffect signal level. PCB 144 may be coupled to assembly 110 by pressfit, adhesive, or other appropriate technique.

PCB 144 includes an aperture 146 through which housing 112, and, hence,shaft 122, pass. PCB 144 also includes inductors 148, which may, forexample, be inductive coils, positioned to electrically respond to themovement of inductive target 142, target 142 and inductors 148 formingan inductive assembly. In particular implementations, inductors 148 maybe cooperating inductive coil elements. These elements may be discreteor printed directly onto PCB 144. Target 142 and inductors 148, alongwith an impressed current from the PCB, generate a change in an eddycurrent pattern in response to the movement of target 142. Eddy currentpatterns may be unique for every for each position corresponding to adifferent temperature value being sensed. PCB 144 additionally includesdetecting circuitry 150 to detect the eddy current patterns and aprocessor 152 to track the movement of the target, and, hence, theshaft, and to determine the sensed temperature based on the movement.Suitable eddy current detecting circuitry is available from LZTTechnology of San Bernadino, Calif. Processor 152 may, for example, be amicroprocessor.

In FIG. 1B, it can be seen that target 142 is in close proximity to PCB144. In this implementation, the distance between target 142 and PCB 144is approximately 0.025 inches. In other implementations, however, target142 does not have to be in close proximity to PCB 144. In general,target 142 may be at any distance as long as it can inductively interactwith inductors 148.

As target 142 begins to rotate in response to rotation of shaft 122, therotation of target 142 relative to PCB 144 causes the eddy currentpattern generated by a predetermined web of target 142 and a facing coilelement instance to change. Processor 152 accumulates these changes,which are analogous to temperature. To accumulate the rotations, theprocessor may understand where the target starts relative to the targetposition and count notches (i.e., pulses) up and down scale. Therequired resolution of the output signal determines the number ofweb/space pairs required in the target.

Coupled to PCB 144 are a pair of wires 158. Wires provide loop power tothe electronic components of PCB 144, such as processor 152. In otherimplementations, PCB 144 may be externally powered.

The temperature measurement device illustrated by FIG. 1 may have avariety of features. For example, the device may allow a relativelysmall inductive target 142 to be used for signal generator 140. Forinstance, the target may have a mass moment of inertia on the order of3.5×10⁻⁵ in-lb, which may, for example, be achieved with a 0.800 inchdiameter×0.007 inch thick aluminum disc with fifty percent gutting.Having a relatively small inductive target may be important because, inmany implementations, the mechanical power generated by assembly 110 issmall. Thus, the temperature may be measured without significantlyinterfering with the mechanical operation of assembly 110. As anotherexample, target 142 may allow inductive current generation across a wideangular range (e.g., three-hundred degrees). This may be important forimplementations where pointer 132 has a wide angular range. As a furtherexample, the signal generator may be used without the visual indicatorassembly. Thus, blind temperature measurement devices are feasible. Asan additional example, the device may be readily manufactured.

Temperature measurement device 100 may have a variety of uses. Forexample, it may be used as a temperature monitoring and reportingdevice. However, it may also be incorporated into other devices thatrequire temperature measurements. For example, device 100 may beincorporated into a temperature correction device adapted to beself-contained in a conventional fluid meter of the fixed or constantdisplacement type.

In particular implementations, a temperature measurement device may haveless, more, and/or a different arrangement of components than device100. For example, assembly 110 may include a low-friction bearingarrangement that supports rotatable shaft 122. In this arrangement,guide 124 may secure shaft 122 in the bearing. Alternatively, a bushingcould be used. As a further example, shaft 122 may be driven by atemperature responsive element other than a bimetallic coil. Forinstance, the shaft may be driven by a gas-filled Bourdon tube connectedto a line and remote-sensing bulb assembly. As an additional example,the inductive target may be directly attached to pointer 132. As anotherexample, a digital indicator may be used in place of the illustratedanalog indicator. In other implementations, though, a visual indicatormay not be used. As a further example, shaft 122 may drive PCB 144rather than inductive target 142. As another example, PCB 144 mayinclude a wireless transmitter to send temperature data to a remotestation. The transmitter could send data using radio frequency (RF),infrared (IR), or any other appropriate technique. Structure may also beprovided in PCB 144 to adjust offset and gain of the signal in knownfashion.

FIG. 2 illustrates an example inductive target 200. Target 200 has a hub210 from which a series of webs 220 radially project. Between webs 220are spaces 230, such that webs 220 and spaces 230 alternate. The totalnumber of webs 220 and spaces 230 is related to the required rotation ofa driving shaft.

In operation, a driving shaft causes target 200 to move relative toinductors on a PCB, which causes the eddy current pattern between a weband facing coil element instance to change. Thus, each web/space pairproduces a pulse under shaft rotation, assuming they are opposite a coilelement. A processor accumulates these pulses and, thus, can determinethe position of the driving shaft. The processor may accumulate theserotations, which are analogous to temperature.

FIG. 3 illustrates a sheath 300 for protecting a temperature-responsiveelement such as a bimetallic coil against injury and improvingperformance. Sheath 300 is formed in a tubular configuration forconnection to a tubular connector flange of a temperature-responsiveassembly, and includes a plurality of a parallel, elongated slots 310through which fluid (i.e., liquid, gas, or a combination thereof) mayflow in contact with a temperature-responsive element. In someimplementations, sheath 300 is removable, which could make it useful forapplications where aperture size varies.

FIG. 4 illustrates an example temperature measurement device 400. Device400 includes a temperature-responsive assembly 410, an inductiveassembly 420, a visual indicator assembly 430, and a sealing assembly440. In operation, temperature-responsive assembly 410 producesmechanical motion in response to temperature changes. The mechanicalmotion drives: 1) inductive assembly 420 such that it produces anelectrical signal corresponding to the sensed temperate; and 2) visualindicator assembly 430 such that it produces a visual indication of thesensed temperature. Sealing assembly 440 protects visual indicatorassembly 430.

In more detail, temperature-responsive assembly 410 includes a stem 412,a coil 414, a shaft 416, and a process connection 418. Stem 412interfaces with the fluid for which the temperature is to be sensed.Located inside stem 412 are coil 414, which may, for example, be abimetallic, spiral-wound coil, and shaft 416. Stem 412 may or may notsealingly protect coil 414 and shaft 416. Coil 414 is coupled to shaft416 and rotates in response to temperature changes. The rotation of coil414 causes shaft 416 to rotate. Shaft 416 passes through processconnection 418 for interaction with other parts of device 400. Processconnection 418 provides a coupling between the fluid process to bemeasured (e.g., fluid in a pipe) and device 400 so that device 400 isnot dislodged due to the movement and/or pressure of the fluid beingmeasured.

Inductive assembly 420 includes a PCB 422 and an inductive target 426.PCB 422 includes an aperture 423 through which shaft 416 passes andinductive coils 424 around aperture 423. PCB 422 is fixed in positionrelative to the shaft. Inductive target 426, on the other hand, iscoupled to the shaft such that it rotates therewith. Thus, when shaft416 rotates, target 426 rotates relative to PCB 422. This rotationinterrupts inductive coils 424, which generates an electrical signalrepresentative of the shaft movement, and, hence, corresponding to thetemperature, as discussed previously.

Visual indicator assembly 430 includes a housing 431 to protect themovable components of the assembly. Assembly 430 also includes a bushing432 that captures shaft 416 and a bearing 433 that couples to the end ofthe shaft to allow it to rotate. Assembly 430 additionally includes agear 434 coupled to bushing 432 and a dial 435 coupled to the gear byscrews 436. Dial 435 includes a dial face 435 a and a dial ring 435 b.Pressure demarcations may be on face 435 a and/or ring 435 b. Coupled tobushing 433 is a pointer 437. Pointer 437 rotates with shaft 416 tovisually indicate the temperature. Assembly 430 additionally includes apinion 438 and an adjuster 439. Pinion interfaces with gear 434 so thatdial 435 may be adjusted by the manipulation of adjuster 439.

Sealing assembly 440 protects components of visual indicator assembly430. Sealing assembly 440 includes a gasket 442, a window 444, and aring 446. To seal assembly 430, gasket 442 is compressed between housing431 and window 444. The compression is maintained by mating ring 446with housing 431. In particular implementations, sealing assembly 440may hermetically seal the visual indicator assembly components insidehousing 431.

FIGS. 5A-B illustrate an example temperature measurement device 500.FIG. 5A shows a top view of temperature measurement device 500, and FIG.5B shows a perspective view temperature measurement device 500.

Device 500 includes a temperature responsive coil 510 that drives ashaft 520. Coupled to shaft 520 is a driving gear 530. Driving gear 530may be made of any suitable material (e.g., metal or plastic) and may berelatively small and lightweight. Device 500 also includes a driven gear540. In general, driven gear 540 has a pitch radius that is larger thanthat of driving gear 530. In the illustrated implementation, forinstance, the pitch radius of driven gear 540 is approximately fifteentimes larger than that of driving gear 530, resulting in a gear ratio ofapproximately 15:1. Driven gear 540 is supported by a pillar 550. Pillar550 is firmly affixed to a printed circuit board 560, which hasinductive coils 562 printed directly thereon. PCB 560 also includes anaperture 564 through which shaft 520 passes. PCB 560 may be rigidlyattached to a tube such as tube 112 in FIG. 1A and/or otherwise isolatedfrom external case strains.

Driven gear 540 includes a tooth section 542 that meshes with drivinggear 530. Driven gear 540 also includes a protuberance 544 that acts asan inductive target for an inductive assembly. If driven gear 540 ismade of plastic then at least one face of protuberance 544 should beoverlaid with a layer of sheet metal (e.g., aluminum) to act as a targetcooperatively functioning with coils 562 to control the eddy currentpatterns. Driven gear 540 further includes apertures 546 to reduce thegear's mass moment of inertia, which allows coil 510 to exert lesstorque to move shaft 520.

Using driving gear 530 and driven gear 540 serves to reduce the rotationof the inductive target (i.e., protuberance 544) to a relatively smallvalue. For example, in the illustrated implementation, the rotation isreduced to approximately 18 degrees when the required pointer rotationis 270 degrees. Another feature is that the motion of the target isalmost linear in nature. This means that the electronic circuitry mayonly have to handle a single, “lengthened” pulse; thus, the circuitrymay not have to count pulses. Hence, this implementation may or may notneed a processor in the circuit design.

FIG. 6 illustrates a process 600 at a temperature measurement device.Process 600 may be implemented by a temperature measurement devicesimilar to device 100 in FIG. 1.

The process begins with waiting to sense a temperature change (decisionblock 604). Temperature may be sensed, for example, by a bimetallic coilor a gas-filled Bourdon tube. Once a temperature change is sensed, theprocess continues with converting the sensed temperature change tomechanical movement (function block 608). The temperature may, forexample, be converted to mechanical movement by a spiral wound,bimetallic coil that causes a shaft to rotate.

The process also calls for converting the mechanical movement to avisual indication of temperature (function block 612). The conversionmay, for example, be accomplished by a pointer coupled to a rotatableshaft and having an accompanying dial.

The process additionally calls for converting the movement to anelectrical signal representing the movement (function block 616). Thismay, for example, be accomplished by an inductive target driven by themechanical movement and inductive coils positioned to electricallyrespond to the target, where eddy current patterns change as theinductive target moves.

After the electrical signal has been generated, the process calls fordetecting the electrical signal (function block 620) and determining themechanical movement based on the electrical signal (function block 624).Determining the mechanical movement may include determining thedirection and magnitude of the movement and may be accomplished bycomparing the electrical signal to previously received electricalsignals to determine a change in amplitude levels.

The process also calls for determining a temperature associated with themechanical movement (function block 628). This may, for example, beaccomplished by an using an algorithmic association of position andtemperature, by consulting a table containing mechanical position andtemperature associations, or by any other appropriate technique. Theprocess additionally calls for generating a signal representing thetemperature (function block 632). The signal may be in analog or digitalformat and may be transmitted using wireline or wireless techniques. Ifin analog form, the signal may be between 4-20 mA. The process thencalls for again waiting to sense a temperature change.

Although FIG. 6 illustrates a process at a temperature measurementdevice, other processes at a temperature measurement device may containless, more, and/or a different arrangement of operations. For example,certain processes may not call for converting the mechanical movement toa visual indication. As another example, the conversion of mechanicalmovement to a visual indication and the conversion of mechanicalmovement to an electrical signal may be accomplished simultaneously. Asa further example, the operations expressed by functions blocks 620-632may be eliminated. As an additional example, some processes may haveoperations that depend on the determined temperature. For instance,temperature check rates and exception reporting may be adjusted based onthe determined temperature. Furthermore, communication rates regardingthe sensed temperature may be adjusted based on the determinedtemperature. For example, as determined temperature rises or falls belowa threshold, communication rates regarding the determined temperaturemay be increased and/or decreased.

While particular implementations and applications have been illustratedand described, it is to be understood that the invention is not limitedto the precise construction and compositions disclosed herein and thatvarious additions, deletions, substitutions, and/or modifications willbe apparent from the foregoing descriptions without departing from thespirit and scope of the invention as defined in the appended claims.

1. A device for measuring temperature, the device comprising: a housing;a temperature-responsive element supported relative to the housing, theelement operable to sense temperature and move in response totemperature changes; a first inductive assembly component fixed relativeto the housing; and a second inductive assembly component operativelyand movably positioned relative to the first inductive assemblycomponent, the second inductive assembly component being driven bymovement of the temperature-responsive element, the movement of thesecond inductive assembly component relative to the first inductiveassembly component generating a change in a local eddy current patterncorresponding to the sensed temperature.
 2. The device of claim 1,wherein a current at a particular point in a sensing circuit isproportional to the temperature changes causing thetemperature-responsive element to move.
 3. The device of claim 1,further comprising a circuit board comprising the first inductiveassembly component.
 4. The device of claim 3, wherein the circuit boardcomprises a processor responsive to generated eddy current patterns togenerate a signal representative of sensed temperature.
 5. The device ofclaim 4, wherein the processor determines the movement of thetemperature-responsive element based on the generated eddy currentpatterns and associates the movement with a temperature to generate thesignal.
 6. The device of claim 1, wherein the temperature-responsiveelement comprises a first portion generally fixed relative to thehousing and a second portion displaceable relative to the first portion,wherein the second portion drives the second inductive assemblycomponent.
 7. The device of claim 6, further comprising a visualindicator movably positioned relative to the housing and driven by thesecond portion of the temperature-responsive element to indicatetemperature.
 8. The device of claim 1, wherein the second inductiveassembly component comprises a gear with a pitch ratio larger than thatof the temperature-responsive element.
 9. The device of claim 8, whereinthe gear comprises a protuberance that operates as an inductive targetin the inductive assembly.
 10. The device of claim 8, wherein the pitchratio of the gear is approximately fifteen times larger than that of thetemperature responsive element.